The invention relates generally to a use of tetraketopiperazine unit-containing compounds as active ingredients in the positive electrodes of batteries and to methods for preparing the tetraketopiperazine unit-containing compounds.
Batteries play an important role within industrialized society. It is estimated that on average ten batteries are used by every person in the United States every year. The economic and environmental impact of this usage is staggering and represents a major point of interest for those in and outside the art.
A battery, in general, is an electrochemical device that generates electric current by converting chemical energy to electrical energy. The essential components of a battery include the positive and negative electrode, a separating medium and an electrolyte. In general, chemically active materials at the negative electrode are oxidized to release electrons which travel to the positive electrode, creating a useable current, where they reduce chemically active materials at the positive electrode. The separating medium keeps the two electrodes insulated from each other, while the electrolyte maintains the oxidizing environment at the negative electrode and the reducing environment at the positive electrode.
Presently, most batteries rely upon chemically active materials that contain metal oxide compounds, due to their excellent oxidizing and reducing capabilities. The metal oxide compounds typically contain manganese, cobalt, nickel, lead, silver, mercury, and the like. Unfortunately, especially in relation to non-rechargeable batteries, or primary batteries, the use of metal oxides represents a large scale environmental problem, where production and disposal of the batteries may result in the release of heavy metals into the environment.
For at least these reasons, there has been an emphasis on developing active materials that limit the use of metal oxides in the electrodes, and in particular, developing organic materials to replace the metal oxides. However, organic materials have proven expensive to produce in the large quantities required for use in battery applications, and have failed to show the requisite electric capacity needed in most battery applications. Synthesis Metals, 1987, 259-264. Against this backdrop the present invention has been developed.
Embodiments of the present invention are directed at novel uses of a compound having at least one tetraketopiperazine-1,4-diyl unit, as represented by formula (1), as an active material in the positive electrodes of batteries. 
Preferable embodiments of the present invention are directed at novel uses of the compound, where the compound has one or two tetraketopiperazine-1,4-diyl units as the active material in the positive electrodes of batteries.
Other embodiments of the present invention are directed at novel uses of a -mono(tetraketopiperazine) compound and di(tetraketopiperazine) compound represented by formulas (1-1) and (1-2), respectively, as active materials in the positive electrodes of batteries. 
R1 and R2 are independently a hydrogen atom or a substituted or unsubstituted alkyl or aryl group. 
R1 and R2 are defined as above and A is a substituted or unsubstituted alkylene or arylene group.
Method A
Other embodiments of the present invention are directed at methods for preparing mono(tetraketopiperazine) compound as represented by formula (1-1) above, by reacting an oxalyl halide represented by formula (2) and an oxamide represented by formula (3), and adding water or an aqueous alkali solution to the reaction mixture. The addition of water or an aqueous alkali solution provides for a substantial increase in the yield of the tetraketopiperazine compound.
X1xe2x80x94COCOxe2x80x94X2xe2x80x83xe2x80x83Formula (2)
The X1 and X2 are independently a halogen atom.
R1xe2x80x94NHxe2x80x94COCOxe2x80x94NHxe2x80x94R2xe2x80x83xe2x80x83Formula (3)
The R1 and R2 are defined as above.
Method B
In another embodiment of the present invention, the mono(tetraketopiperazine) compound represented by formula (1-1) above is prepared by reacting an oxalyl halide represented by formula (2) above and a silylamine represented by formula (4). 
R1 is defined as above and R3, R4, R5, R6, R7 and R8 are independently a substituted or unsubstituted alkyl or aryl group.
Method C
In another embodiment of the present invention, the mono(tetraketopiperazine) compound represented by formula (1-1) above is prepared by reacting an oximidyl halide represented by formula (5) and an amine represented by formula (6). 
R1, X1, and X2 are defined as above. 
R2 is defined as above, and Y1 and Y2 are independently a hydrogen atom, SiR3R4R5, or SiR6R7R8, in which R3, R4, R5, R6, R7 and R8 are independently a substituted or unsubstituted alkyl or aryl group.
Method D
In another embodiment of the present invention, the mono(tetraketopiperazine) compound represented by formula (1-1) above is prepared by reacting an oxalyl halide represented by formula (2) above and a silylamine represented by formula (4) above, and reacting with an amine represented by formula (6) above.
Method E
In another embodiment of the present invention, a di(tetraketopiperazine) compound represented by formula (1-2) above is prepared by reacting an oxalyl halide represented by formula (2) above and a dioxamide represented by formula (7), and, preferably, adding water or an aqueous alkali solution to the reaction mixture.
R1xe2x80x94NHxe2x80x94COCOxe2x80x94NHxe2x80x94Axe2x80x94NHxe2x80x94COCOxe2x80x94NHxe2x80x94R2xe2x80x83xe2x80x83Formula (7)
R1, R2 and A are defined as above.
Method F
In another embodiment of the present invention, the di(tetraketopiperazine) compound represented by formula (1-2) above is prepared by reacting an oximidyl halide represented by formula (5) above and a diamine represented by formula (8). 
A is defined as above, and Y1, Y2, Y3, and Y4 are independently a hydrogen atom, SiR3R4R5, SiR6R7R8, SiR9R10R11, or SiR12R13R14, in which R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13 and R14 are independently a substituted or unsubstituted alkyl or aryl group.
Method G
In another embodiment of the present invention, the di(tetraketopiperazine) compound represented by formula (1-2) above is prepared by reacting an oxalyl halide represented by formula (2) above and a silylamine represented by formula (4) above, and reacting with a diamine represented by formula (8) above.
Finally, in another embodiment of the present invention, oximidyl halide represented by formula (5) above is prepared by reacting an oxalyl halide represented by formula (2) above with a silylamine represented by formula (4) above. The oximidyl halide of formula (5) above is an important intermediate for preparing the mono- and di(tetraketopiperazine) compounds represented by formulas (1-1) and (1-2) above.
Other embodiments of the present invention relates to new compounds produced by the methods of the present invention, which include N,Nxe2x80x2-diethyl-2,3,5,6-tetraketopiperazine, N-alkyl-Nxe2x80x2-aryl-2,3,5,6-tetraketopiperazine, and the di(tetraketopiperazine) compounds represented by formula (1-2) above.
These and various other features as well as advantages which characterize the invention will be apparent from a reading of the following detailed description and a review of the appended claims.